Preparation of oils containing antioxidants



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1.... mm.mia,x.r.,mrmn IJakobsemmnneapoliablinnaa-lgnmtamstillatlonlroductalnclloehestesymfaaeorporation of nelaware t No Application March 8, 1030,Serial No. ems r 5 Claims. (01.260424) rancidity. Oils containing a highcontent oi natural anti-oxidants are of value because of their goodkeeping qualities and also because they are excellent sources ofanti-oxidants. Raw oils usually have an undesirable odor or taste.

Refining removes the taste etc., but also destroys the anti-oxidant.Also raw oils have the defect that they deposit non-volatile residues onthe vaporizing surface of a high vacuum still which residues char andcause destruction of antioxidant and other diiiiculties such as gasformation and foaming. For these reasons high vacuumdistillation torecover anti-oxidant concentrates as described in application 201,018,filed April 8, 1938, in the name of Hickman and Baxter, has in manycases been attended with difiiculties.

Refining methods heretofore known have been found to cause substantialor complete destruction of the natural anti-oxidant content of the oil.For instance, conventional alkali refined oils are almost uniformly freeof natural anti-v oxidant due to destruction caused by the refiningtreatment.

Examples of suitable organic acids are oxalic, tartaric, citric, maleic,adipic, fumaric, malonic,

' phthallc, gacetic, formic, butyric and benzoic acids. Polybasic andespecially diand tri-basic organic acids and their hydroxylatedderivatives are preferred. It is. best when using monobasicorganic acidsto employ those having relatively low molecular weights. Examples ofsuitable weak inorganicacids are boric andortho phosphoric. The latter.represents the strongest inorganic acid which can be used and it causesrather substantial destruction unless used in small amounts at lowtemperatures.

Theacid is added to the oil in the solid or liquid state in which itnaturally occurs or may be added to the oil in aqueous solution which isoften preferred. The oil is then stirred or agitated and may be heatedto elevated temperatures preferably below 100 C. The temperatureemployed will depend upon the particular acid selected. With thestronger acids lower temperatures will be found suitable. The impuritieswillthen have been coagulatedand/or precipitated .and' the oil can bedecanted or directly filtered. Oil purified in this manner is found tobe brighter in color than the crude oil and is free of substances whichharmfully affect the subsequent distillation.

Stale oils or .oils which have been subjected to conventional refiningtreatment contain little or no anti-oxidant and should be avoided assource materials. Raw vegetable and animal oils contain relatively largeamounts of anti-oxidant,

- particularly when freshly removed from the This invention has for itsobject to provide 'methods' for refining anti-oxidant-containing oilswhereby substantial destruction of the antioxidant content is avoided.Another object is to provide a method for refininganti-oxidant-containing oils which results in a refinedv oil containingsubstantially its original anti-oxidant content and which is free ofsubstances which cause charring and foaming during high vacuumdistillation. Another object is to improve the art. Other objects willbecome apparent from the following description and claims.

These and other objects are accomplished in accordance with ourinvention which comprises subjecting the anti-oxidant containing oil toa refining treatment with an organic or weakinor-' 'ganic acid. Oilsrefined by treatment with these materials can be subjected to highvacuum distillation without dimeulty.

source, material. Examples of good. sources of anti-oxidant are cornoil, cottonseed, wheat germ, sesame, clove, thyme, and soy bean oils.

The distillation of the refined oil to concentrate the anti-oxidant iscarried out by heating a thin film of the oil under a high vacuum andcondensing vapors upon a condensing surface separated from the film bysubstantially unobstructed space. 1 The distance between the film andthe condensing surface should be preferably short, such as 1-12 inchesand preferably 1-6 inches, in which case the distillation is known ashigh vacuum. short path distillation. when this distance is less thanthe mean free path of the" residual gas molecules the distillation ismolecular. Pressures below 1 mm. and preferably below .1 mm., such as.01-.0001 mm., are

HOW: I ever, it does not cause char-ring as do the stronger inorganicacids.

I The anti-oxidant'is obtained as a preliminary fractio which distillsimmediately after the free fatty a ds. It is desirable that theanti-oxidant fraction be collected as free of these fatty acids aspossible since they have a pro-oxidant eflect. The temperature at whichthe anti-oxidant fraction is obtained varies considerably depending uponthe pressure and other distillation conditions as well as upon theparticular oil treated. The temperature is generally between 200 and 250and particularly about 210 to 230 under molecular distillationconditions Further details of the distillation procedure etc. will befound in the Hickman and Baxter application referred to above.

When the refined oil is subjected to high vacuum distillation toconceri'trate'the anti-oxidant content thereof, the organic acids willbevolatilized in the early fractions and can thus be separated from theoil. The refined oil should preferably be degassed before introductioninto the still but other treatment is ordinarily unoil which contains anatural anti-oxidant without simultaneously causing substantialdestrucnecessary. Because of the possibility of collecting the organicacids as a first fraction, we prefer to employ these materials asrefining agents. The inorganic acids are not volatile under thedistillation conditions and, therefore, remain in the oil as undistilledresidue. Since these acids are corrosive, it is best to remove them fromthe oil before the distillation treatment.

Example A crude oil which ordinarily deposited. slimy materials on thestill columns was heated at.'70

with .4% of dry oxalic acid for one-half hour.

The major portion of the undesirable materials were coagulated and weredeposited as sludge. The oil was withdrawn and filtered. The filtered.oil was brighter in color and'tests indicated that it contained thefull anti-oxidant potency of the crude oil. J

Oxalic acid is very slightly soluble in oil and .and deposited as asludge, separating the oil' from the impurities, subjecting the oil tohigh vacuum unobstructed path distillation and separating a fraction ofthe oil which contains at least a part of the natural antioxidant.

3. The method of preparing a natural 513'- oxidant concentrate .from avegetable or animal oil which contains a natural anti-oxidant withoutsimultaneously'causing substantial destruction of anti-oxidant whichcomprises in combination, treating the oil with an organic acid wherebythe impurities therein are coagulated, separating the oil from theseimpurities, subjecting it to high vacuum, short path distillation andremoving a fraction containing the anti-oxidant.

4. The process of refining an animal or vegetable oil which contains g.natural anti-oxidant which comprises treating the oil with an organicdibasic acid whereby the impurities are coagu-' lated separating the oilfrom these impurities, subjecting the oil to high vacuum unobstructedpath distillation and separating a fraction of the oil which contains atleast a part of the necessary antioxidant.

5. The process of refining an animal or vegetable oil which,contains anaturalranti-oxidant undoubtedly is present to a slight extent in oilpurified as above. By molecular distillation of the aboveoil the smallamount of oxalic acid was obtained in the first undesired fraction alongwith free fatty acids and other pro-oxidant compounds contained in theoil.

We claim:

which comprises treating the oil with oxalic acid, whereby theimpurities are coagulated separating theoil from these impurities,subjecting the oil to high vacuum unobstructed path distillation andseparating a fraction of the oil which contains atleast a part of thenecessary antioxidant.

1. The method of preparing a natural anti oxidant concentrate from avegetable or animal JAMIES G; BAXTER. JAKQB L. JAKOBSIEN'.

